Modern critical infrastructures, such as water distribution and power generation, are large facilities that are distributed over large geographical areas. Supervisory Control and Data Acquisition (SCADA) networks are deployed to guarantee the correct operation and safety of these infrastructures. In this paper, we describe key characteristics of SCADA traffic, verifying if models developed for traffic in traditional IT networks are applicable. Our results show that SCADA traffic largely differs from traditional IT traffic, more noticeably not presenting diurnal patters or self-similar correlations in the time series.